Embedded Real time Operation System (RTOS).Embedded system It is "a device used to control, monitor or assist in the operation of machines and equipment"
Embedded Real-time Operation System，It is abbreviated as (RTOS)
System definition
When external events or data are generated, they can be accepted and processed at a fast enough speed, and the processing results can control the production process or make rapid response to the processing system within the specified time, and control the coordinated operation of all real-time tasksEmbedded operating system。
Note: In industrial control, military equipment, aerospace and other fields, there are strict requirements for system response time, which requires the use ofreal-time system 。The embedded operating system we often talk about is embeddedreal-time operating system 。such asμC/OS-II, eCOS, Linux and HOPEN OS. Therefore, the understanding of embedded real-time operating system should be based on the understanding ofEmbedded system Add the requirements for response time to the understanding of.
IEEE Definitions
Embedded system Yes "Devices used to control,monitor, or assist the operation of equipment, machinery or plants”。
It is a special computer system with application as the center, computer technology as the foundation, software and hardware can be cut, function, reliability, cost, volume and power consumption are strictly required.
background
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With the rapid development of computer technology and the continuous progress of chip manufacturing technology,Embedded system The application of embedded systems has become increasingly widespread: embedded systems can be found everywhere, from civil television, mobile phones and other circuit equipment to military aircraft, tanks and other weapon systems.In the application development of embedded system, embeddedreal-time operating system (RTOS for short) can support multiple tasks, making program development easier, easier to maintain, and improving the stability and reliability of the system.This has gradually becomeEmbedded system developmentA development direction of.
Development history
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In 1981, Ready System developed the world's first commercial embedded real-time kernel (VRTX32), and today it has a history of nearly 20 years.In the 1980s, products only supported 16 bitmicroprocessor, such as 68k, 8086, etc.At this time, RTOS only had the kernel to sellBinary codeMainly.In addition to VRTX, there were MTOS of IPI and PSOS of ISI in the late 1980s.The products are mainly used for military and telecommunication equipment.In the 1990s,Modern operating systemDesign ideas, such asMicrokernelDesign technology andModular designThought began to infiltrate into the RTOS field.Old RTOS manufacturers such as Ready System (merged with Microtec Research in 1995) also introduced a new generation of VRTXsa real-time kernel, and a new generation of RTOS manufacturer Windriver introduced Vxwork.In addition, during this period, all companies strive to get rid of the restriction of completely relying on third-party tools, and form a complete development environment by purchasing, authorizing or using free tool chains.For example, Prismt of ISI, the famous Tornado (Windriver) and the old brand Spectra (VRTX development system).
In the mid-1990s, the trend of the Internet became increasingly popular in North America.Network equipment manufacturers and terminal product manufacturers all require RTOS to have network and graphical interface functions.To facilitate the use of a large number of existingSoftware codeThey hope that RTOS manufacturers support standard APIs, such as POSIX, Win32, etc., and that the RTOS development environment is consistent with the UNIX and Windows they are already familiar with.Typical products in this period include Vxwork, QNX, Lynx, WinCE, etc.
technological development
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It can be seen that after the 1990s, RTOSEmbedded System DesignThe dominant position of RTOS has been determined. More and more engineers use RTOS, and more new users are willing to choose to buy rather than develop it themselves.We have noticed the following changes in the technical development of RTOS:
1. Because there are more and more new processors, the design of RTOS's own structure is easier to transplant, so as to support more microprocessors in a short time.
2. The wind of open source has spread to RTOS manufacturers.When a considerable number of RTOS manufacturers sell RTOS, they attach source code and include production royalties.
3. In the post PC era, more products use RTOS, which does not require high real-time performance, such as handheld devices.MicrosoftWinCE, Plam OS, Java OS and other RTOS products are developed in compliance with these applications.
4. Telecommunication equipmentControl systemThe requirement of high reliability puts forward new requirements for RTOS.SwedenEnea's OSE and WindRiver's new Vxwork AE support HA (high availability) andHot switchAnd other characteristics.
5. Windriver has acquired ISI, which has formed a considerable monopoly in the RTOS market. However, because Windriver has decided to give up PSOS and develop the integrated version of Vxwork and PSOS, PSOS users have once again come to the intersection of re selecting RTOS, giving other RTOS manufacturers a chance.
6. Embedded Linux has been applied in consumer electronic devices.Some enterprises in South Korea and Japan have launched handheld devices based on embedded Linux.Embedded Linux is supported and invested by a wide range of semiconductor manufacturers, such as Intel and Motorola.
Future applications
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RTOS can be divided into three different areas:
1. System level: RTOS runs in a small computer system to complete real-time control.This field will mainly be the place where Microsoft competes with Sun. Traditionally, Unix has an absolute advantage here.Through acquisition, Sun has combined Solaris with Chorus os (the original RTOS in Europe), and Microsoft has pushed the embedded version of NT "Embedded NT".In addition, embedded Linux will rely on the advantages of open source code and rich software resources to enter the system level RTOS market.
2. Board level: the main market of traditional RTOS.For example, applications of Vxwork, PSOS, QNX, Lynx and VRTX will mainly focus on aerospace, telephone and telecommunications equipment.
3. SOC level (i.eSystem on chip）: The field of new generation RTOS: mainly used in consumer electronics, Internet, handheld devices and other products.The representative products include Symbian Epoc, ATI Nucleus, and Express logic Threadx.VRTX and Vxwork products of old RTOS manufacturers also pay attention to this market.
To some extent, there will not be a standard RTOS (like Microsoft's Windows in the desktop system), because embedded applications are extremely diverse.In a certain period of time and industry, there will be an absolute leading RTOS, such as today's Vxwork in broadband data communication equipment and WinCE in the Asian handheld device market.However, this monopoly is not unbreakable, because users and partners are more willing to cultivate a new competitor to some extent.For example, Montivista invested by Intel and Lineo invested by Motorola, the two embedded Linux systems, indicate that semiconductor manufacturers are more willing to see an affordable and open RTOS environment.
Current situation in China
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China will be one of the largest RTOS markets in the world.Because China has the largest telecom market in the world.According to the prediction of the Ministry of Information Industry, in the next 2-3 years, China will be the world's largest mobile phone market (each mobile phone is running one RTOS).
Such a huge telecom market will breed a large number of telecom equipment manufacturers, which creates a large number of RTOS and development tool market opportunities.Until 2013, most equipment manufacturers in China have first considered foreign products when adopting RTOS.
At present, RTOS popular in the Chinese market mainly includes Vxwork, PSOS, VRTX, Nucleus, QNX and WinCE.Since most RTOS are embedded in the controller of the device, most users are not willing to take risks to try a new RTOS.
However, we also noticed that the sales of RTOS in the Chinese market are still very small, mainly for two reasons:
1. The scale of Chinese equipment manufacturers is generally not comparable to that of foreign companies, and the development and personnel costs are relatively high, so RTOS is relatively expensive for Chinese users.
2. Most domestic users have not yet started to purchase the royalties of RTOS. The main reasons are that the products are not produced in batches as planned and they have no awareness of paying royalties.It should be noted that most binary RTOS must pay royalties when the product is mass produced, or buy by quantity or discuss a one-time buyout with the manufacturer, and the manufacturer will directly send you a license agreement.According to a foreign RTOS manufacturer, 30% of their annual income comes from royalties.
Classification Introduction
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μTenux
μTenux[1]It is an open source and free hard real-time embedded operating system. The development team is from Dalian, mainly targeting the microcontroller of ARM Cortex M0-M4 series.Its kernel adopts μ T Kernel which appeared in the 1980s.In Japan, the most developed embedded country in the world, μ T Kernel accounts for 60%.At the same time, the open source community of tecoss China also launched Tenux, the R series and A series for ARM Cortex.At present, Youlong Software is a partner of ARM, a world famous company, or of Ti, ATMEL, ST, T-Engine, Neusoft, Tianfusoftwarepark, TEG, Parasoft etc. chip manufacturers.[1]
At present, the official stable version code of μ Tenux is V1.5.00r160.[1]
DJYOS
DJYOSIt is an embedded real-time operating system, which is not considered to be compatible withwindows、linux、unixCompetition.
The DJYOS operating system is scheduled based on events. This scheduling strategy enables programmers to program according to the habits of human beings rather than computers.
In ordinary operating systems, scheduling is centered on threads. Events are regarded as thread data, and the software model labeled as "event triggering" is also waiting by threads. When a specific event occurs, threads resume running and process it as input data.
Event centered scheduling, like devices and memory, treats the threaded virtual machine as the resource needed to process events. When an event needs to be processed, allocate or create a threaded virtual machine to the event, and start the threaded virtual machine to process the event.
In the embedded field,DJYOSTo be compatible with non real-time operating systems such aslinux、winceCompetition, and real-time operating systems such asvxworks、qnxCompetition.
DJYOS aims to change the situation that China has no (influential) operating system. In the near future, one of the world's popular operating systems will come from China.
VxWorksreal-time operating system It is composed of more than 400 relatively independent and short target modules. Users can select appropriate modules to cut and configure the system according to their needs;Provide priority based task scheduling, synchronization and communication between tasksInterrupt processing、timerandmemory management And other functions, built-in POSIX compliant (portableOperating system interface）Standard memory management and multiprocessor control program;And it is concise and easy to understandUser interfaceIn terms of core, it can even be shrunk to 8 KB.
μC/OS-II
μ C/OS-II is developed on the basis of μ C-OSEmbedded system An expert Jean J. Labrosse wrote a compactPreemptive The multitasking real-time kernel of.μ C/OS-II can manage 64 tasks and provide task scheduling and managementmemory management , inter task synchronization and communication, time management, interrupt service and other functions, with the characteristics of high execution efficiency, small space occupation, good real-time performance and strong scalability.
μClinux
μClinuxIt is an excellent embedded systemLinux version, its full name is micro control Linux, which literally means micro control Linux.Compared with standard Linux, μ Clinux's kernel is very small, but it still inheritsLinux operating system, including good stability and portability, powerful network functions, excellent file system support, standard rich APIs, andTCP/IP network protocolEtc.Because there is no MMUmemory management Therefore, the implementation of its multi task needs some skills.
eCos
ECos (embedded configurable operating system) is an embedded configurable operating system.It is asource codeOpen, configurable, portable, and deep embedded application orientedreal-time operating system 。The biggest feature is flexible configurationModular designThe core part consists of Xiaotong's components, including the kernel, the C language library and the underlying running package.Each component can provide a large number of configuration options (the real-time kernel can also be used as an optional configuration). It can be easily configured using the configuration tools provided by eCos, and eCos can meet different embedded application requirements through different configurations.
RTXC
RTXC is the abbreviation of Real Time eXecutive in C language.It is a flexible, industrial application tested multitask real-time kernel, which can be widely used in various 8/16 bit applicationssinglechip16/32 bitsmicroprocessorEmbedded applications of DSP processors."After several years of investigation, the China SCM Public Laboratory believes that it is more suitable for China's national conditions, and introduces the" embedded system "into the Chinese marketReal time multitasking operating systemEither.
